请问5509A读取SD卡阻塞该怎么办？

SD卡是1G的FAT32格式的
我是调用CSL库函数进行操作的，在例程中加入MMC_read函数程序貌似就卡住了，查看了下网上的资料感觉像是阻塞，具体现象如下：
正常现象：
MMC Controller setup test...
SD card found
Asking SD card for its RCA...
RCA sent is 0xb368
Initialized card successfully
TEST PASSED
加了MMC_read函数的现象
MMC Controller setup test...
SD card found
Asking SD card for its RCA...
RCA sent is 0x

程序代码：
void main()
[
  Uint16 mybuf[256],i,mybuf1[256];
  CSL_init();
  PLL_config(&myConfig);
  printf ("MMC Controller setup test...n");
  mmc0 = MMC_open(MMC_DEV1);
  MMC_setupNative(mmc0,&Init); //initialize the MMC controller
//  MMC_getConfig(mmc0,&test);
  MMC_sendGoIdle(mmc0); //Sends a broadcast GO_IDLE command
  for (count=0;count<4016;count++)
  asm("       NOP");
  cardtype = MMC_sendOpCond(mmc0,0x00100000); //Sets the operating voltage window while in Native mode
  if (cardtype == 0xFFFF)[
   printf ("Card not recognizedn");
   exit(0);
  ]
  //MMC_setCardType(card, cardtype);
  if (cardtype == MMC_CARD)[
   printf ("Setting 10 as RCA valuen");
   cid = &cardid;
   /* Instruct all cards to send their Card Identification Data */
   MMC_sendAllCID(mmc0,cid); // get the CID structure for all cards.
   card = &cardalloc;
   //retVal = MMC_setRca(mmc0,card,0x8DAB);
   retVal = MMC_setRca(mmc0,card,2);
   /* The host can request for the CSD in the standby state. This *
   * structure contains the data outlined below                   */
   printf ("Reading CSD structure for MMC cardn");
   csd = &cardcsd;
   retVal=MMC_sendCSD(mmc0);
   MMC_getCardCsd(mmc0, csd);
  ] else [
   printf ("SD card foundn");
   cid = &cardid;

   /* Instruct all cards to send their Card Identification Data */
   SD_sendAllCID(mmc0,cid);
//    printf ("The values in the CID of the SD card are:n");

   printf ("Asking SD card for its RCA...n");
   card = &cardalloc;
   rca = SD_sendRca(mmc0,card);
   printf ("RCA sent is 0x%xn", rca);

   /* The host can request for the CSD in the standby state. This *
   * structure contains the data outlined below                   */

   retVal = MMC_sendCSD(mmc0);
//    sdcsd = &sdcardcsd;
//    SD_getCardCsd(mmc0, sdcsd);
  ]

  retVal = MMC_selectCard(mmc0,card);
  MMC_read(mmc0,0x238200,mybuf,256);
  for(i=0;i<6000;i++);
  printf ("Initialized card successfullyn");
  printf ("TEST PASSEDn");
  while(1);

]